Re: Fixed size vector

From:
Andrea Crotti <andrea.crotti.0@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 28 Oct 2010 11:26:25 +0200
Message-ID:
<m17hh21xdq.fsf@ip1-201.halifax.rwth-aachen.de>
Andrea Crotti <andrea.crotti.0@gmail.com> writes:

I would need something in theory quite simple, a vector of a certain
size, which, when I add something and it's full, simply deletes the last
entry.

If for example I have

MyContainer x(3);
x.push(1);
x.push(2);
x.push(3);
x.push(4);

it should contain now
<4, 3, 2>

I don't see any of the STL structures doing exactly what I would like,
any suggestions on how to implement it?


The whole story (which is maybe more helpful) is that I have a vector of
vectors of a certain maximal size
<1, 2, 3>
<2, 2, 3>
....
and I have to compute a vector which is the average of all of them.
Now what I did is a vector of vectors and using a map to count up the
values for after doing the average

--8<---------------cut here---------------start------------->8---
    // if it's a landmark one 0 should always be so
    std::map<coord_t, int> land_hops;
    for (int i=0; i < history_size; ++i) {
        for (int j=0; j < address[i].getSize(); ++j) {
            coord_t hop_count = address[i][j];

            // if it's not reachable or == 0 then it should not be inside the average
            if (hop_count > 0) {
                if (land_hops.count(j) == 0) {
                    land_hops[j] = hop_count;
                } else {
                    land_hops[j] += hop_count;
                }
            }
        }
--8<---------------cut here---------------end--------------->8---

but it's really ugly and not very smart probably, better ideas??

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